Tendency to Explode
by slackerD
Summary: high school AU, Follows One Benefit to Detention and Hiding Behind Science. When assigned to build a rocket powered by water, Cosima decides to use a different approach.


**Title:** Tendency to Explode  
**Author:** slacker_d  
**Pairing/Characters:** Sarah/Cosima  
**Summary:** high school AU When assigned to build a rocket powered by water, Cosima decides to use a different approach.  
**Disclaimer:** Not mine.  
**Word Count:** ~1,530  
**A/N:** Follows One Benefit to Detention and Hiding Behind Science.

* * *

"All right class," Mr. Peckham says once everyone has settled down. "We're going to have a little competition this week."

The reaction is a mixture of grumbles and excitement.

"I promise you that this one will be more fun than the egg drop challenge," he vows.

"Wouldn't take much," someone quips from the back of the room.

"And once again, there is a prize."

This earns a few half hearted cheers and whoops.

"So this week, you all get to build rockets—" Mr. Peckham pauses as heartfelt cheering erupts. Once the room quiets, he continues. "However, because things some times have a way of starting on fire..."

Every head in the room swivels to glare at Cosima. If she didn't know any better, she'd think they planned it. She just waves and offers a cheeky grin.

Mr. Peckham coughs and gains the classes attention. "The rockets will be powered by water."

A few people boo.

"I know," he says. "But that's how it has to be." He glances around the room. "I'm glad to see that you all managed to find a two liter bottle to bring in." He then sets a foot pump, a roll of plastic tubing and a foot long cooper pipe onto his desk. "We're going to place each of your rockets on this pipe, lock it in place, pump it full of air and then release it. It should launch into the air because of the pressure build up."

"So how do we win?" someone calls out.

"The competition part," Mr. Peckham says. "Is whose rocket flies the highest. So your job is to make this rocket as aerodynamic as possible. You have three days."

**…**

When the bell rings, everyone hurries out, knowing they have to get to their next class. Cosima hangs back and approaches Mr. Peckham's desk.

"No, you are not the sole reason that we're using water as fuel," he says before Cosima can speak.

"Way to burst that bubble," Cosima pouts. "Are you telling me I wield less power than I thought?"

"How can I help you Ms. Niehaus?"

"Would it be possible for me to build a different type of rocket?"

"Explain."

"I'd still use water as the fuel," Cosima replies. "And I'd still use the two liter bottle as the rocket."

Mr. Peckham stares at her for a moment as she tries to not bounce with eagerness. "Dare I ask what you're thinking?"

Cosima just grins and lays out her plan.

**…**

This certainly isn't the first time Sarah's stayed after school because Cosima wants to explain a science project to her. However, this might be the most excited she's ever seen her.

Sarah's not quite sure what she's looking at. On the table is a car battery with jumper cables attached. However, the other ends of the cables have alligator clips that are attached to wires that are jammed into rubber corks. The corks are plugging up the bottoms of two tall glass tubes filled with water. There are actually three vertical glass tubes connected by one horizontal one. But only the two other ones have corks. The outer two also have funnels on the top of them, with the narrow stems pointing upwards. Each funnel has a plastic tube attached that lead into the mouth of an empty two liter bottle. The amount of duct tape around the tubes and opening of the bottle seems excessive to Sarah, but since she's not quite sure what Cosima is doing, she probably should withhold judgment. The middle tube has a large funnel in it, with the wide part sticking out and it's filled with water.

"So what exactly are you doing?" Sarah asks.

Cosima grins. "So we're supposed to be making rockets that are powered by water," Cosima starts.

"Okay..."

"So this is a Hofman Electrolysis Apparatus. I'm using electrolysis to separate this water into hydrogen and oxygen atoms," Cosima continues.

"You're what?"

Cosima points to one of the rubber corks. "Do you see all this copper at the bottom here?"

Sarah nods.

"This side is gathering all the hydrogen, which rises into the funnel, through the plastic tube and into the bottle," Cosima explains. "And on this side, we have zinc, which is gathering all the oxygen and that is also collecting in the bottle."

"Because..."

"Because if I collect enough oxygen and hydrogen in this bottle and then add a spark to it, there should be an explosion of sorts as they try to reform water."

"And that's going to make your rocket fly?" Sarah clarifies.

Cosima nods. "It should fly the higher and longer than the ones just powered by water pressure build up.

"Oh. Cool."

"Mr. Peckham says that whoever's rocket goes the highest gets a prize," Cosima adds.

"Did he say what the prize is?" Sarah asks. "What if it's something lame? Like a prism or something?"

"Last time it was two movie vouchers," Cosima replies.

"Did you win last time?" Sarah questions.

"No that was the time when my supposedly heat proof glass beaker broke."

"Yeah?"

"At least no one got hurt," Cosima shrugs.

"I guess that's why Peckham chose water as a fuel?" Sarah questions. "Less chance of you blowing something up or hurting someone?"

"Well, he claims otherwise," Cosima replies. "But I'd like to think I had something to do with it."

**…**

Three days later, everyone gives Cosima a wide berth as she carries her rocket outside—which is ridiculous since at the moment, it's just a plastic bottle of oxygen and hydrogen. Besides, she's too excited to care and since Mr. Peckham doesn't seem too concerned, Cosima figures she has the competition already won since everyone else is relying purely on aerodynamics for height.

Mr. Peckham has connected the copper tube to a square of plywood with legs. The plastic tubing is attached to the bottom and eventually connects to the foot pump. There's a small claw with an arm that is affixed to a hinge which is nailed to the plywood. The string that's tied around the arm is just as long as the plastic tubing, so that when there's enough air pressure built up, the string can be pulled to launch the rocket. It's rather crude and Cosima wonders who built the odd apparatus in shop class for extra credit.

Cosima requires a different sort of launch pad, which she sets up. First she opens the tripod. Then she attaches the copper pipe. She places her bottle over the copper pipe. which fits snugly in the mouth of the bottle. The other end of the pipe has been clamped except for a tiny opening where the wire from the igniter that's inside the pipe can get out. The wire is long enough that Cosima can stand several feet back, push the red button and cause the spark she needs to launch her rocket.

Once she's set up, she turns to Mr. Peckham and nods.

Since everyone assumes that something will go wrong with Cosima's, they vote that she should go last, because no one wants to miss the chance to try out their rocket before Cosima's explodes or starts a fire.

One by one her classmates launch their rockets. The rest of the class judges and there's no clear winner. So Cosima gets ready, feeling confident that she's going to win. She approaches her launch pad, grabs the red button, counts down from three and presses.

There's a loud explosion and then the bottle just sort of melts.

As she and Mr. Peckham examine her rocket, they realize it just got too hot, too quickly and so the plastic melted. Cosima lets out a sigh of frustration. She put a lot of effort into this rocket.

Mr. Peckham assures her that she'll still be getting an A, since it's obvious the science worked—perhaps a little too well. Meanwhile, behind them, Cosima can hear her classmates settling their bets. She rolls her eyes, hating how predictable she's apparently become.

**…**

When the final bell rings, Sarah finds Cosima at her locker.

"So I heard that your rocket launch didn't quite happen," Sarah teases.

"I overestimated how much force I'd need," Cosima replies as she slams her locker door shut.

"Too bad," Sarah says, taking Cosima's hand as they start to walk down the hall. "I was looking forward to a free movie."

"Who said I was taking you?" Cosima grins, letting their arms swing slightly as they walk.

"Who else are you going to make out in the back with?"

"Well..."

Sarah stops walking and glares. "You better not be making out with anyone else."

"Well, Scott did win," Cosima grins. "I bet he'd take me to a movie." She starts walking again, tugging Sarah along, their fingers still entwined.

"Keep saying shit like that and I'll be forced to do something drastic," Sara grumbles, letting herself be pulled forward.

Cosima stops and spins around, hand still wrapped around Sarah's. "Oooh, color me intrigued," she grins.

Sarah sighs and steps around Cosima, stomping down the hall. Her hand is still clenched in Cosima's, so she has a giggling girlfriend trailing behind her. It really ruins her dramatic exit.


End file.
